Add field trial for enabling Stage3D in XP

chrome/browser/chrome_gpu_util.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chrome_gpu_util.h"
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/version.h"
@@ skipping 104 matching lines @@
       content::kGpuCompositingFieldTrialThreadEnabledName,
       threaded_compositing_probability);
 
   bool force_compositing = (trial->group() == force_compositing_group);
   bool thread = (trial->group() == thread_group);
   UMA_HISTOGRAM_BOOLEAN("GPU.InForceCompositingModeFieldTrial",
                         force_compositing);
   UMA_HISTOGRAM_BOOLEAN("GPU.InCompositorThreadFieldTrial", thread);
 }
 
+bool ShouldRunStage3DFieldTrial() {
+#if !defined(OS_WIN)
+  return false;
+#else
+  if (base::win::GetVersion() >= base::win::VERSION_VISTA)
+    return false;
+  return true;
+#endif
+}
+
+void InitializeStage3DFieldTrial() {
+  if (!ShouldRunStage3DFieldTrial()) {
+    base::FieldTrial* trial =
+        base::FieldTrialList::Find(content::kStage3DFieldTrialName);
+    if (trial)
+      trial->Disable();
+    return;
+  }
+
+  const base::FieldTrial::Probability kDivisor = 1000;
+  scoped_refptr<base::FieldTrial> trial(
+    base::FieldTrialList::FactoryGetFieldTrial(
+        content::kStage3DFieldTrialName, kDivisor,
+        content::kStage3DFieldTrialEnabledName, 2013, 3, 1, NULL));
+
+  // Produce the same result on every run of this client.
+  trial->UseOneTimeRandomization();
+
+  // Kill-switch, so disabled unless we get info from server.
+  int blacklisted_group = trial->AppendGroup(
+      content::kStage3DFieldTrialBlacklistedName, kDivisor);
+
+  bool enabled = !(trial->group() == blacklisted_group);

[Alexei Svitkine (slow), 2012/09/19 21:12:36]

Nit: bool enabled = (trial->group() != blacklisted_group);

+
+  UMA_HISTOGRAM_BOOLEAN("GPU.Stage3DFieldTrial", enabled);
+}
+
 // Load GPU Blacklist, collect preliminary gpu info, and compute preliminary
 // gpu feature flags.
 void InitializeGpuDataManager(const CommandLine& command_line) {
   if (command_line.HasSwitch(switches::kSkipGpuDataLoading))
     return;
 
   std::string chrome_version_string = "0";
   std::string gpu_blacklist_json_string;
   if (!command_line.HasSwitch(switches::kIgnoreGpuBlacklist)) {
     chrome::VersionInfo chrome_version_info;
     if (chrome_version_info.is_valid())
         chrome_version_string = chrome_version_info.Version();
 
     const base::StringPiece gpu_blacklist_json(
         ResourceBundle::GetSharedInstance().GetRawDataResource(
             IDR_GPU_BLACKLIST, ui::SCALE_FACTOR_NONE));
     gpu_blacklist_json_string = gpu_blacklist_json.as_string();
   }
   content::GpuDataManager::GetInstance()->Initialize(
       chrome_version_string, gpu_blacklist_json_string);
 }
 
 }  // namespace gpu_util;